Explosive forces and high pressure shock pulses caused by an explosive device or system such as ordnance (e.g., projectiles, bombs, missiles, etc.) or another type of gas or chemical explosion, whether intentional or accidental, may cause substantial damage, injuries, and death. Blast dissipative structures are becoming increasingly desired for use in protecting items of value from the effects of such high pressure impulses.
In order to be effective, blast dissipative structures must absorb and dissipate significant amounts of energy to prevent damage from the pressure impulse generated by an explosion. Concrete has been employed in the past to make a passive standoff barrier to withstand the destructive force of an explosion, such as the detonation of a bomb. However, barriers made from concrete take time to construct and once constructed are permanent. Also, rigid concrete barriers do not absorb or dissipate shock pressure effectively. Instead, such barriers efficiently transmit the incident shock pressures through the barrier and apply pressure loading to the elements disposed on the other side of the barriers. As the result of the efficient transmission of the shock pressure pulse, rigid concrete barriers may spall and create harmful flying debris and/or may, in later time, crumble and create damaging falling debris. One method to absorb pressure pulses created by explosion has been to use water filled barriers. Blast dissipative structures using water-based technology are disclosed, for instance, in U.S. Pat. No. 4,836,079. As disclosed therein, bomb blast inhibitors can be inflated with air, placed around a bomb, and then filled with water, the water then acting to suppress or otherwise mitigate against the effects of any ensuing explosion. However, use of liquids having a relatively low viscosity (e.g., water) generally, if permitted, will flow to the regions of lowest potential energies as directed by gravity. Consequently, the use of such liquids requires that the liquid be contained in a desired initial configuration and limits the configuration and application of structures utilizing such a liquid. Moreover, the barrier needs to be erected where there is an adequate water supply. The barriers are often bulky which can pose transportation problems and add to the cost of using them and render them undesirable for utilization by a vehicle or by personnel.
Other attempts to provide blast dissipative structures are described in U.S. Pat. Nos. 7,575,797 and 6,200,664. 7,575,797 describes a blast reducing structure including a plurality of webs forming discrete funnel-shaped container elements containing volumes of liquid or deformable materials, such as liquids or materials. The liquid or deformable materials in the discrete container elements are constrained initially by a grommet, plug, or other sealing member and flow upon rupture from impact pressures. Alternate container elements formed by the webs are air-filled so as to accept the expelled liquid from adjacent container elements. The liquids or deformable materials flow through apertures formed in each of the plurality of webs to absorb impact energy.
U.S. Pat. No. 6,200,664 describes a structure for containing an explosion including a plurality of truncated polyhedral container elements secured to and projecting from a base sheet. Each polyhedral element is filled with a liquid, such as water, and is constructed to collapse in the event of an explosion. An opening in each of the polyhedral container elements is sealed by a burst disk or a removable seal that opens in the event of an explosion. The opening is sized to effect a misting action of the liquid therein when it is ejected from the openings by the collapse of the polyhedral container elements caused by the explosion. The liquid mist serves to absorb and dissipate the heat and energy of the explosion.
As mentioned above, each of the devices described in U.S. Pat. Nos. 7,575,797 and 6,200,664, utilize single rows of discrete container elements having a flowable liquid or deformable material disposed therein. Such elements require the use of a sealing member, such as a plug to contain the liquid or deformable material within the element prior to impact. Furthermore, the single rows of sealed, discrete container elements only expel the liquid or deformable material into an adjacent volume or element. During an impact, such configurations will only release the liquid or deformable materials from the container elements that were directly contacted by the impact of the force with sufficient magnitude. The liquid or deformable materials could also be released accidentally by evaporation and expansion of the liquid and gas.